Low Energy Dissipation Research Articles

Reversible nanorouter using QCA for nanocommunication

In reversible nanocomputing, an emerging area of research is quantum dot cellular automata (QCA)-based design of cost-effective reversible nanocircuits. In a digital nanocommunication system, the router is the heart of data transmission. At nanoscale, for data communication the device density and energy dissipation of the circuit are key issues. A reversible circuit exhibits low energy dissipation or ideally no energy dissipation. This paper presents the design of a Fredkin gate- and a BJN gate-based design of reversible 4:1 multiplexer and 1:4 demultiplexer based on QCA with quantum costs of 15 and 30 respectively and garbage output of six and ten respectively. The proposed reversible multiplexer and demultiplexer are used to achieve a reversible nanorouter in QCA for the first time, with a quantum cost of 40 and garbage output of 16. The proposed reversible nanorouter could be used to achieve a nanocommunication system in the near future at the nanoscale low energy level. A QCA device is used to implement the proposed reversible circuits, to achieve a low-energy nanoscale circuit. The comparison of simulation consequences of proposed circuits with theoretical knowledge established the functional efficiency of the circuit.

Theoretical model for multiple breakup of fluid particles in turbulent flow field

Generalized phenomenological model, based on the theories of probability and isotropic turbulence, is developed for multiple breakup of fluid particles in turbulent flow field. The approach uses a series of successive binary breakup events occur at a time scale comparable to the colliding eddy turnover time. It was found that the use of energy density, instead of energy, will increase the predicted binary breakup rate which is usually underestimated by the existing models in the literature. Generalization of the binary breakup model for multiple fragmentations is performed by defining a “remaining energy function” for the colliding eddy which means the contribution of original eddy to the later breakup events. For ternary breakage, the model shows a reasonably good agreement with the experimental data. The quaternary fragmentation frequency, however, is of negligible importance at lower energy dissipation rates but its contribution to breakage fraction at higher energy dissipation rates becomes considerable. The results also show that ternary and quaternary breakups have a considerable 90% contribution to the overall fragmentation, while pentenary and further fragmentations are of lower importance at low energy dissipation rates. At higher levels of energy dissipation rate, fragmentations up to six daughter particles contribute to more than 95% of the overall fragmentations. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4508–4525, 2016

HEATING AND ACCELERATION OF THE FAST SOLAR WIND BY ALFVÉN WAVE TURBULENCE

ABSTRACT We present numerical simulations of reduced magnetohydrodynamic (RMHD) turbulence in a magnetic flux tube at the center of a polar coronal hole. The model for the background atmosphere is a solution of the momentum equation and includes the effects of wave pressure on the solar wind outflow. Alfvén waves are launched at the coronal base and reflect at various heights owing to variations in Alfvén speed and outflow velocity. The turbulence is driven by nonlinear interactions between the counterpropagating Alfvén waves. Results are presented for two models of the background atmosphere. In the first model the plasma density and Alfvén speed vary smoothly with height, resulting in minimal wave reflections and low-energy dissipation rates. We find that the dissipation rate is insufficient to maintain the temperature of the background atmosphere. The standard phenomenological formula for the dissipation rate significantly overestimates the rate derived from our RMHD simulations, and a revised formula is proposed. In the second model we introduce additional density variations along the flux tube with a correlation length of 0.04 R ⊙ and with relative amplitude of 10%. These density variations simulate the effects of compressive MHD waves on the Alfvén waves. We find that such variations significantly enhance the wave reflection and thereby the turbulent dissipation rates, producing enough heat to maintain the background atmosphere. We conclude that interactions between Alfvén and compressive waves may play an important role in the turbulent heating of the fast solar wind.

Experimental investigation on hysteretic behavior of thin-walled circular steel tubes under constant compression and biaxial bending

This paper presents a comprehensive experimental and numerical investigation on hysteretic behavior of thin-walled circular steel tubes as loaded members in reticulated shells. The experimental setup available for constant compression and biaxial bending loading was designed to examine the failure process, failure modes, load bearing capacity, ductility, stiffness degradation and energy dissipation capacity of sixteen thin-walled circular steel tubes. Also, the effects of the loading condition, axial load ratio, slenderness and steel strength on hysteretic behavior of specimens were investigated. The study showed that test results of specimen loaded in two directions might overestimate hysteretic characteristic of this member. Premature local buckling may be caused by the high axial load ratio and the recommended axial load ratio may be n ≤ 0.2 to ensure the load bearing capacity, deformation capacity and ductility of circular steel tubes and to prevent the premature local buckling occurring in engineering practice. Slenderness affects the load bearing capacity, ductility, and energy dissipation capacity of specimens, and with an increasing slenderness, the stiffness degraded considerably and quickly. Specimens with high strength steel exhibited higher load bearing capacity and better stiffness but lower energy dissipation capacity than those made by low strength steel. Furthermore, the nonlinear finite element analysis was performed to simulate hysteretic behavior of test specimens, and the results got a satisfactory agreement with those of test.

Punching behaviour of RC flat slabs under reversed horizontal cyclic loading

The aim of this work is to study the behaviour of reinforced concrete flat slab structures under combined vertical and horizontal cyclic loading. A total of five specimens were cast and tested: a control specimen was punched without eccentricity, one specimen was tested under constant vertical loading and monotonically increased eccentricity until failure and the remaining three were tested under constant vertical load, at different shear ratios, and cyclic horizontal loading with increasing horizontal drift ratios. All slabs were similar, measuring 4.25×1.85×0.15m3. The reinforced concrete slab specimens were connected to two steel half columns by 0.25×0.25m2 rigid steel plates, prestressed against the slab using steel bolts, to ensure monolithic behaviour. The cyclic tests were performed using an innovative test setup that allows bending moment redistribution, line of inflection mobility, assures equal vertical displacements at the North-South borders and symmetrical shear forces. Results show that cyclic horizontal actions are very harmful to the slab–column connection, resulting in low horizontal drifts and energy dissipation.

Monotonic and cyclic response of speed-lock connections with bolts in storage racks

The purpose of this paper is to explore the bearing capacity and energy dissipation of several variations of speed-lock connections of cold-formed steel storage racks. Commonly used speed-lock connection exists large slippage and low energy dissipation capacity, new speed-lock connections with additional bolts (and welds) are investigated in order to enhance its performance. Their monotonic behavior and hysteretic response under cyclic loading were studied experimentally using a cantilever test method. The tests were conducted using both the EN 15512 monotonic protocol and AISC seismic provisions’ cyclic-test protocol for each specimen. The failure modes, moment–rotation response, and associated stiffnesses, bearing capacities, and energy dissipation capabilities were fully investigated. Both monotonic and cyclic responses showed that the additional bolts (and welds) significantly enhanced the bearing capacities and deformability of the connections, though the initial stiffness and equivalent stiffness (i.e., according to the EN 15512 specification) showed little improvement. The hysteretic responses of all connection variations investigated demonstrated pinching behaviors. The energy dissipation capability has been greatly improved with additional bolts (and welds) except of the one with only lower bolts, which could also be corroborated through the analyses of the calculated equivalent viscous damping coefficient and the displacement ductility factor. In addition, the stiffness degradation has been observed for both positive loading and negative loading, and adding bolts and welds could effectively reduce this effect.

Effects of the magnitude and persistence of turbulence on phytoplankton in Lake Taihu during a summer cyanobacterial bloom

Turbulence, a ubiquitous feature of geophysical fluids and highly variable both in space and time, is a major driver of change in both physicochemical characteristics and phytoplankton communities of the water column. The effects, however, of the magnitude and persistence of turbulence on phytoplankton community structure and dynamics of harmful algal blooms are still poorly understood in lakes. To explore the importance of the kinetic energy and duration of turbulence in phytoplankton, a 15-day mesocosm experiment was carried out and tested under four turbulence regimes namely calm water (control), low (energy dissipation rate, ɛ = 1.12 × 10−6), medium (ɛ = 2.95 × 10−5 m2 s−3) and high (ɛ = 1.48 × 10−4 m2 s−3) turbulence, which are comparable to the natural hydrodynamic conditions in Lake Taihu. Results showed that turbulences promoted the growth of phytoplankton and shifted the phytoplankton community structure from being cyanobacteria-dominated (Microcystis spp.) to diatom-dominated (Fragilaria spp.) community after a lag phase of 8–11 days. However, before the 6th day, the biomass of Microcystis spp. was dramatically promoted under turbulent conditions. These findings suggest that the dominance of diatom may be independent within a certain range of turbulent kinetic energy under constant turbulence conditions. This study suggests that short-term (<6 days) turbulence, regardless of its kinetic energy, is beneficial for the cyanobacterial harmful algal blooms (CyanoHABs) in eutrophic lakes.

Dynamic tensile properties of bovine periodontal ligament: A nonlinear viscoelastic model

As a support to the tooth, the mechanical response of the periodontal ligament (PDL) is complex. Like other connective tissues, the PDL exhibits non-linear and time-dependent behavior. The viscoelasticity of the PDL plays a significant role in low and high loading rates. Little information, however, is available on the short-term viscoelastic behavior of the PDL. Also, due to the highly non-linear stress–strain response, it was hypothesized that the dynamic viscoelastic properties of the PDL would be greatly dependent on the preload. Therefore, the present study was designed to explore the dynamic tensile properties of the bovine PDL as a function of loading frequency and preload. The in vitro dynamic tensile tests were performed over a wide range of frequencies (0.01–100Hz) with dynamic force amplitude of 1N and different preloads of 3, 5 and 10N. The generalized Maxwell model was utilized to describe the non-linear viscoelastic behavior of the PDL. The low loss factor of the bovine PDL, measured between 0.04 and 0.08, indicates low energy dissipation due to the high content of collagen fibers. Moreover, the influence of viscous components in the linear region of the stress–strain curve (10N preload) was lower than those of the toe region (3N preload). The data reported in this study could be used in developing accurate computational models of the PDL.

Filler Wetting in Miscible ESBR/SSBR Blends and Its Effect on Mechanical Properties

The selective wetting behavior of silica in emulsion styrene butadiene rubber (ESBR)/solution styrene butadiene rubber (SSBR) blends is characterized by the wetting concept, which is further developed for filled blends based on miscible rubbers. It is found that not only the chemical rubber–filler affinity but also the topology of the filler surface significantly influences the selective filler wetting in rubber blends. The nanopore structure of the silica surface has been recognized as the main reason for the difference in the wetting behavior of the branched ESBR molecules and linear SSBR molecules. However, the effect of nanopore structure becomes more significant in the presence of silane. It is discussed that the adsorption of silane on silica surface constricts the nanopore to some extent that hinders effectively the space filling of the nanopores by the branched ESBR molecules but not by the linear SSBR molecules. As a result, in silanized ESBR/SSBR blends the dominant wetting of silica surface by the tightly bonded layer of SSBR molecules causes a low-energy dissipation in the rubber–filler interphase. That imparts the low rolling resistance to the blends similar to that of a silica-filled SSBR compound, while the ESBR-rich matrix warrants the good tensile behavior, i.e., good abrasion and wear resistance of the blends.

Population balance modeling of precipitated calcium carbonate (PCC) flocculation induced by cationic starches

In order to predict and control the flocculation process, it is necessary to develop quantitative model which can describe aggregation, breakage and restructure phenomenon. In this paper, population balance equation was employed to model the PCC flocculation process. Energy dissipation rate was calculated to evaluate the floc strength. It was found, compared to the low charge density starch, the high charge density starch resulted in lower collision efficiency, lower restructure rate and stronger flocs (indicated by higher energy dissipation rate). The higher the temperature, the lower the energy dissipation rate was needed to break the flocs. The addition of NaCl did not show effect on the collision efficiency for both high and low charge density starches, but weaker flocs were formed and more prominent restructure rate was observed at higher NaCl concentration. The collision efficiency decreased with the increase of the shear rate for both starches. At higher starch dosage, lower energy dissipation rate could break the flocs and higher restructure rate was observed.

Switching characteristics of all spin logic devices based on Co and Permalloy nanomagnet

The need for low-power alternatives to digital electronic circuits has aroused the increasing interest in spintronic devices for their potentials to overcome the power and performance limitations of (CMOS). In particular, all spin logic (ASL) technology, which stores information using the magnetization direction of the nano-magnet and communicates using spin current, is generally thought to be a good post-CMOS candidate for possessing capabilities such as nonvolatiliy, high density, low energy dissipation. In this paper, based on nano-magnetic dynamics described by Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation and transport physics of spin injection and spin diffusion, a coupled spin-transport/magneto-dynamics model for ASL is established. Under different channel lengths and applied voltages, the switching characteristics of ASL device comprised of Co and Permalloy (Py) nano-magnets are analyzed by using the coupled spin-transport/magneto-dynamics model. The results indicate that the switch delay, energy dissipation and thermal noise effect of PyASL are lower than those of CoASL. The main reason is that the saturation magnetization of Py is less than that of Co. Under the same applied voltage, the maximal channel length of PyASL is longer than that of CoASL when ASL device can switch accurately. Moreover, the two ASL devices' switching delay can be reduced by reducing channel length or increasing applied voltage, and the energy dissipation can be reduced by reducing channel length or applied voltage, whereas there are no optimized applied voltages to minimize the energy-delay product. In addition, the influences of thermal noise on switching delay and energy dissipation can be improved by lowering channel length, but increasing applied voltage can only improve the influence of thermal noise on switching delay. The above-mentioned conclusions will supply essential guidelines for optimizing the ASL devices' materials and configuration.

Epitaxial patterning of nanometer-thick Y3Fe5O12films with low magnetic damping

Magnetic insulators such as yttrium iron garnet, Y3Fe5O12, with extremely low magnetic damping have opened the door for low power spin-orbitronics due to their low energy dissipation and efficient spin current generation and transmission. We demonstrate here reliable and efficient epitaxial growth and nanopatterning of Y3Fe5O12 thin-film based nanostructures on insulating Gd3Ga5O12 substrates. In particular, our fabrication process is compatible with conventional sputtering and lift-off, and does not require aggressive ion milling which may be detrimental to the oxide thin films. Their structural and magnetic properties indicate good qualities, in particular low magnetic damping of both films and patterned structures. The dynamic magnetic properties of the nanostructures are systematically investigated as a function of the lateral dimension. By comparing with ferromagnetic nanowire structures, a distinct edge mode in addition to the main mode is identified by both experiments and simulations, which also exhibit cross-over with the main mode upon varying the width of the wires. The non-linear evolution of dynamic modes over nanostructural dimensions highlights the important role of size confinement to their material properties in magnetic devices where Y3Fe5O12 nanostructures serve as the key functional component.

Effectiveness of body bias and hybrid logic: an energy efficient approach to design adders in sub-threshold regime

Rapid increases in chip complexity, increasingly faster clocks and proliferation of portable devices have combined to make power dissipation an important design parameter. In battery operated digital devices the demand of low power consumption and low energy dissipation in order to maximise battery life are the matter-of-course. Typical energy optimisation measures include voltage scaling and operating at the slowest possible speed. In this paper, to satisfy the low power requirement, sub-threshold logic that involves scaling voltage below the device threshold is being used. The proposed implementation lays emphasis on the usage of hybrid logic with reverse body biasing schemes which reduces high power consumption while giving lesser propagation delay and lesser area in sub-threshold regime. This scheme has been demonstrated on 4-bit, 16-bit and 64-bit carry look-ahead adders and simulated using TSMC 180 nm CMOS technology at 0.4 V supply voltage. Post-layout simulations show significant improvement, exhibiting low power consumption and lesser propagation delay as compared to conventional carry look-ahead adder.

Experimental Research on Variable Hydraulic Resistors of Servo-hydraulic Valves

For the nowadays industry, the hydrostatic actuation is indispensable, thus reducing the energy losses in valves that control the parameters of hydraulic energy, it has become an area of interest in applied research. The paper aims to conduct a study on hydraulic resistors, following the hydrodynamic forces that appear in an adjustable valve like a load for the valve actuator. Three types of holes (circular, rectangular, triangular) for the sleeve were assembled with each of the three spools chamfered at different angles resulting different geometry for the active edge. The results show that the variant in which the openings are rectangular and the edge of the piston is tapered at an angle of 60°, develop the lower hydrodynamic force and thus lower energy dissipation. The paper presents the experimental setup used, which offers the possibility of monitoring also the noise during operation, being able to establish the time of cavitation occurrence using spectral analyzes. The optimizations achieved by reducing the hydrodynamic forces, are important in terms of energy.

Adhesive contact of a power-law graded elastic half-space with a randomly rough rigid surface

A theoretical model of a power-law graded elastic half-space in contact with a randomly rough rigid surface is established by combining the Greenwood–Williamson rough contact model and the JKR type adhesion model for power-law graded materials. The rough surface is modeled as an ensemble of non-interacting asperities with identical radius of curvature and Gaussian distributed heights. By applying the JKR type theory for power-law graded solids to each individual asperity of the rough surface, the total normal forces for the rough surface are derived for loading and unloading stages, respectively, and a prominent adhesion hysteresis associated with dissipation energy is revealed. Our results include the solutions for homogeneous materials and Gibson solids as special cases and describe the complete transition between these two limiting situations. A dimensionless adhesion parameter, which influences both the total pull-off force and the energy dissipation due to adhesive hysteresis, is also identified. It is found that a small adhesion parameter results in higher energy dissipation and pull-off force, while a large adhesion parameter leads to lower energy dissipation and pull-off force.

Digital image correlation analysis of strain recovery in glassy polymer network isomers

Digital image correlation techniques were applied to compressive strain recovery experiments of glassy network isomers to study architectural contributions to deformational response. Strain recovery experiments provided a direct comparison of network isomer structure on viscoelastic deformation. Diglycidyl ether of bisphenol-A (DGEBA) was cured with 3,3′- and 4,4′-diaminodiphenyl sulfone (33DDS and 44DDS). The comparison revealed the networks have similar elastic and plastic strain components, but differ in anelastic strain response. DGEBA cured with 44DDS developed pre-yield anelastic strain at a significantly higher rate attributed to increase in free volume, molecular motions and energy dissipation. In contrast, DGEBA cured with 33DDS displayed lower pre-yield energy dissipation attributed to lower free volume and molecular motions, but exhibited a higher degree of post-yield strain-softening due to larger segmental rearrangements.

Ultralow Friction with Hydrophilic Polymer Brushes in Water as Segregated from Silicone Matrix

Lubrication is essential to minimize damage to underlying material and ensure low energy dissipation in biological and man‐made mechanical systems. Surface grafting of hydrophilic polymer brushes is a powerful means to render materials that are slippery in aqueous environments. However, presently available approaches to graft polymer brushes on surfaces, e.g., “grafting‐from” or “grafting‐to” approaches, display several restrictions in terms of practical and long‐term applications. Here a unique method of forming hydrophilic polymer brushes by selective segregation of hydrophilic chains of amphiphilic diblock copolymers, such as poly(dimethylsiloxane)‐b‐poly(ethylene glycol) (PDMS‐b‐PEG) and poly(dimethylsiloxane)‐b‐poly(acrylic acid) (PDMS‐b‐PAA) from the PDMS matrix with an “inverted grafting‐to” approach, and its tribological applications, is presented. In this approach, as the hydrophilic polymer brushes are generated from an internal source of the material, excellent grafting stability and restoring capabilities are revealed even under harsh tribostress. The film can easily be applied to elastomers, metals, and ceramic substrates by spin‐ or drip‐coating. Obtained sliding friction coefficients (μ) are 0.001–0.05 for soft contacts depending on substrate, load, counter surface, pH, and salinity. Between the two types of hydrophilic polymer chains, PAA shows far superior lubricity compared to PEG, which is rationalized by the larger reduction of total free energy of the former upon hydration.

Temperature-Stable, Energy-Efficient, and High-Bit Rate Oxide-Confined 980-nm VCSELs for Optical Interconnects

We report 980-nm VCSELs that achieve temperature-stable, energy-efficient, and high-bit rate data transmission concurrently. Oxide-aperture-dependent static characteristics and high-speed modulation properties are analyzed at room temperature and also at high temperature. It is demonstrated that VCSELs with oxide-aperture diameters smaller than ∼5 μm are most suitable to achieve energy-efficient, temperature-stable, and high-bit rate operation concurrently. We demonstrate error-free data transmission (defined as a bit error ratio < 1 × 10 −12) at 38 Gb/s from 25 to 85 °C without any change of working point and modulation condition by using VCSELs with oxide-aperture diameters smaller than 5 μm. For VCSELs smaller than ∼7 μm, 42 Gb/s error-free data transmission at 25 °C is achieved. Record low energy dissipation at 85 °C is achieved with our ∼3 μm oxide-aperture diameter VCSELs. At room temperature, only 145, 147, and 217 fJ of dissipated heat energy per bit is needed for 35, 38, and 42 Gb/s error-free data transmission. Each of these bit rates is a record low heat dissipation for 980-nm VCSELs. Our VCSELs are especially well suited for very short reach (<2 m) optical interconnects in high-performance computers, for board-to-board and chip-to-chip input/output interfaces and data buses, and for on-chip integrated photonics.

Numerical comparison of the seismic performance of steel rings in off-centre bracing system and diagonal bracing system

During a seismic event, a considerable amount of energy is input into a structure. The law of energy conservation imposes the restriction that energy must either be absorbed or dissipated by the structure. Recent earthquakes have shown that the use of concentric bracing system with their low ductility and low energy dissipation capacity, causes permanent damage to structures during intense earthquakes. Hence, engineers are looking at bracing system with higher ductility, such as chevron and eccentric braces. However, braced frame would not be easily repaired if serious damage has occured during a strong earthquake. In order to solve this problem, a new bracing system an off-centre bracing system with higher ductility and higher energy dissipation capacity, is considered. In this paper, some numerical studies have been performed using ANSYS software on a frame with off-centre bracing system with optimum eccentricity and circular element created, called OBS_C_O model. In addition, other steel frame with diagonal bracing system and the same circular element is created, called DBS_C model. Furthermore, linear and nonlinear behavior of these steel frames are compared in order to introduce a new way of optimum performance for these dissipating elements. The obtained results revealed that using a ductile element or circular dissipater for increasing the ductility of off-centre bracing system and centric bracing system is useful. Finally, higher ductility and more energy dissipation led to more appropriate behavior in the OBS_C_O model compared to DBS_C model.

User Authentication Based on Quantum-Dot Cellular Automata Using Reversible Logic for Secure Nanocommunication

QCA is a new nanodevice to achieve logic circuit at nanoscale level. User authentication is a key issue in nanocommunication, to allow only authorized user to access data. Excessive heat dissipation of irreversible process caused the circuitry bound of CMOS-based circuit. Reversible logic is an alternative to these problems. Reversible circuits have very low heat energy dissipation which is ideally zero. This paper illustrates an optimized design of Fredkin gate using QCA. The proposed Fredkin gate has outshined the existing circuits in terms of area, cell count, and latency. The design of reversible user password authenticator circuit has been explored based on Fredkin gate. The quantum cost of this authenticator circuit is five. For the first time, QCA layout of proposed user authenticator is also achieved in this paper. The quantum cost of QCA-based authenticator circuit is 0.041. All the QCA circuits are precise in terms of QCA cell, device density, and clocking zones, i.e., latency. Theoretical values are compared with simulation results that justify the design accuracy of the proposed circuits. The computational functionality of the circuit under thermal randomness is estimated which establishes the stability of the proposed circuit. The estimation of energy dissipation proves that the proposed circuit dissipates very low energy. To achieve low-power nanoscale authenticator circuit, QCA is used to implement the reversible logic.